Fabrication of porous polymer films is important for its potential applications in industry and everyday life. In this study, a thermoresponsive polymer poly(N-isopropylacrylamide-co-butylmethacrylate) (PNIBMA) was introduced to fabricate porous films on the glass surface. PNIBMA can alter its structure with temperature and has a lower critical solution temperature (LCST) of about 20 °C. The porous film of PNIBMA was prepared by drying a drop of PNIBMA solution (in CHCl₃) on a glass surface under a moist air flow. Atomic force microscope (AFM) images showed that the porous polymer film contained many layers of vacant spheres with diameters of about 1 μm. This unique surface characteristic endowed the porous film with higher hydrophobicity than a flat PNIBMA film made by direct coating. This study expanded the materials for porous films fabrication in the field of thermoreponsive polymers and should be of great potential in scientific researches and industry applications.